Solid surfaces of glass, plastics, paper, textile products, metals and the like are often imparted with water repellency but are rarely imparted with oil repellency. However, in cases where a more pronounced anti-fouling effect against oil stains or the like needs to be imparted to such surfaces, it is desirable that the surface exhibits both a large contact angle and a small sliding angle not only with water, but also with low-surface tension substances typified by oils. Specifically, there is a demand for the formation of a coating film that combines both water repellency and oil repellency. Further, the coating film should preferably combine both high water repellency and high oil repellency, i.e. superhydrophobicity and superoleophobicity.
Patent Document 1 discloses a coating solution obtained by dispersing hydrophobic microparticles having an average primary particle size equal to or smaller than 100 nm in an organic solvent that contains 65 mass % or more of a hydrophobic solvent with respect to the total organic solvent. Patent Document 1 describes that a coating film formed by using the coating solution exhibits a contact angle of 140 degrees or more with water.
Patent Document 2 discloses a coating film having a root-mean-square surface roughness (RMS) of 100 nm or greater, obtained through application of a coating composition that comprises an alcohol, an alkoxysilane, a perfluoroalkyl silane, silica microparticles, a catalyst that promotes the hydrolysis reaction of the alkoxysilane, and water. Patent Document 2 indicates that a coating film formed using that coating solution exhibits a contact angle of 150 degrees or more with water and 130 degrees or more with oils.
Patent Document 1: Japanese Patent Application Laid-open No. 2010-155727
Patent Document 2: Japanese Patent Application Laid-open No. 2010-89373